Mass-energy distribution of fragments in Langevin dynamics of fission induced by heavy ions

Abstract

Abstract. Four-dimensional Langevin equation was employed to calculate mass-energy distributions of fission fragments of highly excited compound nuclei. The research took into account not only three shape collective coordinates introduced on the basis of {c, h, α}-parametrization but also orientation degree of freedom (K-state) -spin about the symmetry axis. Overdamped Langevin equation was used to describe the evolution of the K-state. Friction tensor was calculated using the "wall+window" model of the modified one-body dissipation mechanism with a reduction coefficient from the "wall" formula k s . The calculations have been performed with k s = 0.25 and k s = 1.0. To learn more about the role of the dissipation effects the calculations have also been done with use of the chaoticity measure of nucleon movements in the nuclear shape configuration as k s parameter. Calculations were performed for the large number of compound nuclei with Z 2 /A parameter in the range 21 Z 2 /A 44. The goal was to study the mass-energy distributions not only for heavy nuclei but also for light nuclei close to the Businaro-Gallone point. Mass-energy distributions and variances of the mass fragments are well reproduced in the applied calculations for all considered compound nuclei. It was shown that inclusion of the K-state in the dynamical model produces considerable increase of the mass and energy variances. Inclusion of the chaoticity measure to the friction tensor provides a better agreement with the experiment results on mass variances.

Investigation of dissipation in the tilting degree of freedom from four-dimensional Langevin dynamics of heavy-ion-induced fission

“…In particular, we investigate the effect of the deformation dependence of the γ K coefficient on the fission fragment MED parameters, prescission neutron multiplicity, and anisotropy of the fission fragment angular distribution. This study will help us to determine how the results of recent 4D calculations [13,14,[19][20][21] performed with a constant γ K would change in case of deformation-dependent γ K coefficient.…”